The present invention pertains to a heater, especially a water or air heater operated with liquid fuel for a motor vehicle in the form of an auxiliary heater or a parking heater, with a housing jacket and a heat exchanger as well as with a control device for regulating and monitoring the heating operation by means of at least one temperature sensor, especially a regulating temperature sensor and/or an overheating sensor.
A temperature sensor in the form of a regulating temperature sensor, which is preferably arranged in the air or water channel in the area of the heat exchanger and is an actual value transducer of a control circuit, is used for the space temperature control in vehicle heaters of the above-mentioned type. The control device regulates the heating output in such a way that the space temperature corresponds to the preset set point with the smallest possible deviation. Another temperature sensor in the form of an overheating sensor, which is located at a suitable hot point in the heater, especially in the dome area of a heat exchanger, is used for the upward limitation of the temperature of the heater by switching off the heater in order to rule out a state of overheating in the heater.
It is disadvantageous that the regulating temperature sensor and the overheating sensor are prefabricated as separate components with rather long cables, contacts and individual lead insulation and are arranged, sent for mounting and mounted individually and stocked as separate components. The two sensors are identical components and can be easily transposed at the plug of the control device.
Based on the above-mentioned state of the art, the object of the present invention is to improve a heater of the type mentioned in the introduction such that it can be mounted simply, rapidly and reliably and is nevertheless reliable in operation.
According to the invention, a heater, especially a liquid fuel-operated water heater or air heater of a motor vehicle in the form of an auxiliary heater or a parking heater is provided. The heater has a housing jacket and a heat exchanger as well as a control device for regulating or monitoring the heating operation. At least one temperature sensor is provided, especially a regulating temperature sensor and/or overheating sensor. The temperature sensor is arranged on the underside of a control device bottom plate facing the housing jacket and extends through an opening of the housing jacket, especially a water jacket, in the direction of the heat exchanger.
As a result, the overheating temperature sensor and/or temperature sensor can be mounted on the underside of the control device bottom plate already at the time of the manufacture of the control device and the final mounting of the prefabricated control device bottom plate with the connected temperature sensor on the heater can be performed easily and rapidly with the positioned ID temperature sensor. The opening in the housing jacket is used as the positioning aid.
The temperature sensor, which is fixed on the underside of the control device bottom plate and is connected to the control device bottom plate, is preferably accommodated displaceably in the opening of the housing jacket which is designed as a fitting opening. As a result, fine positioning of the temperature sensor is possible. In addition, the depth of extension of the temperature sensor in the direction of the heat exchanger can be set exactly.
The temperature sensor preferably has a fitting housing part with a circumferential recess, the outer circumference of the fitting housing part being accommodated in a sliding fit in the fitting opening. As a result, the pushing in of the temperature sensor into the fitting opening is facilitated and jamming or tilting is minimized.
A sealing ring, which ensures good sealing of the mediumxe2x80x94air or waterxe2x80x94which is guided in the heater, is preferably located in the housing recess.
Provisions are made in an especially expedient embodiment variant for the temperature sensor and the control device bottom plate to be supported on a protective housing of the control device via a compression spring located in the control device. In the installed state of the temperature sensor or sensor, it is thus guaranteed that, e.g., expansions (movements) of the heat exchanger caused by temperature variations can be absorbed without damage to the sensor, the control device or the heat exchanger.
The housing jacket preferably has, in the axial extension of the fitting opening, a radially outwardly directed projection, which is located away from the fitting opening and on which the control device bottom plate is flatly supported. A close contact is obtained for the control housing bottom plate as a result. In addition, the control device bottom plate can be arranged at a spaced location from the housing jacket, preferably parallel to the axis. The distance creates a heat-insulating air gap between the housing jacket and the control device bottom plate.
The control device bottom plate is advantageously also pressed to the projection by the force of the compression spring. The mounting of the control device bottom plate is further simplified as a result in case of sufficient seating of the control device bottom plate in the control device.
The control device bottom plate is preferably supported at the projection loosely, especially in an axially displaceable manner. As a result, the control device bottom plate, which is fixed in the installed position by the opening of the housing jacket and the temperature sensor passed through there, can be mounted at the projection in a stress-free manner in the anal direction. A possible thermal expansion is thus compensated with certainty.
A pressing plate, which absorbs the compressive force of the compression spring and distributes it two-dimensionally in the control device bottom plate, maybe fastened on the top side of the control device bottom plate in the area of the compression spring as a protection for the control device bottom plate.
The top side of the pressing plate preferably contains an axial guide for the compression spring, especially a fitting recess, which positions the compression spring in the installed state.
In particular, the top side of the control device bottom plate is arranged at a spaced location from the protective housing in order to create an installation space for electronic components, which are preferably fastened and connected on the top side of the control device bottom plate.
The temperature sensor preferably has at least one connection cable, which is plugged, soldered or connected in another way to the underside of the control device bottom plate in such a way as to establish a connection. The connection cable can have a short length as a result. Individual seals are eliminated.
The temperature sensor may be spring-pretensioned at a radially inner stop of the heater by the force of the compression spring. The radially inner stop may be a shoulder or a taper in the opening of the housing jacket.
However, the radially inner stop is especially preferably a jacket surface of the heat exchanger itself, which is especially a contact surface of the temperature sensor, whose temperature is to be monitored. A reliable, clearance-free and stress-free contact is thus established between the temperature sensor and the heat exchanger with simple means, without the risk of damage to the sensor during operation due to possible temperature variations or thermal expansions.
The temperature sensor may be an individual sensor, especially an overheating temperature sensor or a regulating temperature sensor, and a plurality of temperature sensors, which are located at mutually spaced locations from one another and extend through corresponding openings in the housing jacket, may also be arranged on a single control device bottom plate.
The temperature sensor is preferably a combination sensor, which contains the overheating sensor and the regulating temperature sensor as one assembly unit, which offers advantages in from manufacture and mounting. Thus, overheating sensors and regulating temperature sensors cannot be transposed with one another during the mounting, either.
The protective housing itself is firmly and water-tightly connected, especially screwed to the housing jacket.
The present invention advantageously leads ultimately to a reduction in the costs of parts and mounting.
The present invention will be explained in greater detail below on the basis of an exemplary embodiment with reference to the attached drawing that schematically shows an axial vertical section of the right upper area of a heater.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming apart of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which a preferred embodiment of the invention is illustrated.